1. Field of the Invention
This invention relates generally methods for measuring electrical resistance and more particularly, to methods for measuring electrical resistance in tires across parts of tires.
2. Description of the Related Art
Moving vehicles may experience a buildup of static electricity of relatively high voltage unless a grounding path is provided to dissipate the charge. Such charge buildup is undesirable for a number of reasons including, for example, having an adverse impact on the vehicle's electronic circuitry, e.g., its radio reception and having an adverse impact on an occupant of the vehicle when the occupant experiences an electrical shock upon providing a path to ground for the built-up charge, typically upon the occupant entering or exiting the vehicle.
To prevent the buildup of the static electricity in the vehicle, the charge may be dissipated by providing a continuous ground to earth from the vehicle. Previously, particularly for larger vehicles, a ground was provided by dragging along a chain or other electrical conductor connected to the frame of the vehicle. As the vehicle moved, a charge was conducted to the ground along the chain.
Preferably, tires can provide the path to ground for dissipating the electrical charge. However, not all materials that might be used in tire construction are necessarily electrically conductive. Rubber compositions that are electrically conductive are typically constructed from compounds having significant proportions of conductive carbon black. Conversely, rubber compositions that are relatively nonconductive tend to have significantly larger amounts of silica relative to carbon black since, increasing the relative proportion of silica relative to carbon black typically decreases conductivity.
It is desirable, therefore, for tire manufactures to provide tires that dissipate any static electricity to ground to prevent the buildup of charge in the vehicle. Determining whether a tire has an adequate design for such dissipation is desirable.